The present application relates to an optical information recording method, an optical information reproducing method, an optical information recording apparatus, and an optical information recording and reproducing apparatus by which information is recorded by irradiating a medium with light.
As an example of a technique that dramatically increases recording capacity of an optical recording medium, a volume recording type optical recording medium in which a recording region is expanded in the thickness direction is proposed (for example, Japanese Unexamined Patent Application Publication No. 2008-071433). A recording material of this optical recording medium is a resin material which is a transparent for recording light and reproducing light. As a method for densely forming a recording mark within a transparent resin material, recording light having a wavelength of 405 nm is focused on a desired position and thus the optical intensity is increased on the position so as to develop a non-linear optical effect of the resin material, that is, to develop two-photon absorption and absorb light. A method for forming a void (hole) within a recording material by the two-photon absorption is proposed (for example, Japanese Unexamined Patent Application Publication No. 2009-238282).
In this two-photon absorption phenomenon, absorption efficiency is commonly increased in proportion to a square of optical energy.
The two-photon absorption phenomenon was theoretically proposed by Goeppert-Mayer from Germany in 1931 and was substantiated in an experiment in 1961 (for example, Maria Goeppert-Mayer, Ann. Phys. 9 (1931) 273). This phenomenon is developed by radiating light having a single wavelength and good coherency such as laser light in large optical intensity.